Qualitative dynamics of wavepackets in turbulent jets

TL;DR

This paper investigates the complex temporal behavior of wavepackets in turbulent jets using experimental data, statistical analysis, and modeling to determine the necessity of nonlinear models for accurate description.

Contribution

It provides a qualitative analysis of wavepacket dynamics and compares linear and nonlinear models to assess their effectiveness in capturing these dynamics.

Findings

Nonlinear models may be necessary for accurate wavepacket dynamics

Statistical tools estimate embedding and correlation dimensions

Linear models offer a control-oriented perspective

Abstract

It has long been established that turbulent jets comprise large-scale coherent structures, now more commonly referred to as "wavepackets". These structures exhibit a remarkable spatio-temporal organisation, despite turbulence. In this work we analyse, from a qualitative point of view, the temporal dynamics of axisymmetric wavepackets educed, experimentally, from subsonic iso-thermal jets. We use the data presented by, where time-series of the wavepackets are extracted at different streamwise locations. A thorough analysis is performed, statistical tools are used for estimating the embedding and correlation dimensions characterising the dynamical system. System identification is used for computing nonlinear surrogate models. Finally, control-oriented linear models are computed. The goal of the contribution is to assess the extent to which non-linear models are necessary, or appropriate, for description of the temporal wave-packet dynamics and to provide a complementary perspective to the current modelling.